Combine the vermouth, Soya or Tamari sauce, water and ginger in a bowl and mix well.
Put the fish in a dish and pour in the marinade, covering the fish completely.
Cover with a sheet of aluminum foil and place in the refrigerator for 2 hours (or preferably, overnight), turning the fish over twice while refrigerating.
Oil a dripping pan or the barbecue grill and cook the fish over medium heat (or at 160Â°C/325Â°F in the oven) for 4 minutes on each side or until the fish becomes opaque.
Combine the ingredients for the sauce in a bowl and mix well.
Pour over the fish and serve.